The present invention relates to a hydraulic circuit for traveling in which two hydraulic motors for driving the traveling wheels can be rotated by employing one hydraulic pump.
A related hydraulic circuit for traveling in which two hydraulic motors for driving the traveling wheels are rotated by one hydraulic pump is, for example, shown in FIG. 3.
This hydraulic circuit comprises: a hydraulic pump 11; two hydraulic motors 14, 15 for driving and rotating the traveling wheels 12, 13, respectively; a pumping passage 16; a flow dividing valve 17; and an opening-closing valve 19. The pumping passage 16 comprises one end connected to the hydraulic motor pump 11 and is bifurcated halfway to provide other ends respectively connected to the hydraulic motors 14, 15 so as to supply a high pressure fluid discharged from the hydraulic pump 11 to the two hydraulic motors 14, 15. The flow dividing valve 17 serving to supply an equal amount of fluid to the hydraulic motors 14, 15 is provided at the branch portion of the pumping passage 16. The opening-closing valve 19 is interposed halfway in a connection passage 18 for connecting the bifurcate portions 16a, 16b in the pumping passage 16.
And in this hydraulic circuit, if anyone of the traveling wheel, for example, a traveling wheel 12, may float due to the rough road surface, the load exerting on the hydraulic motor 14 becoming quite small, almost all amount of the high pressure fluid discharged from the hydraulic pump 11 is supplied to the hydraulic motor 14, so that the traveling wheel 12 is skidding to make traveling impossible.
In this case, by switching the opening-closing valve 19 from an open to closed state, the flow passing areas of the bifurcate portions 16a, 16b are controlled by the flow dividing valve 17 in accordance with the loads applied on the hydraulic motors 14, 15, so that the high pressure fluid from the hydraulic pump 11 is supplied in equal amount to the hydraulic motors 14, 15 to continue the traveling.
In the related hydraulic circuit, the flow dividing valve 17 is used to supply an equal amount of high pressure fluid to the hydraulic motors 14, 15. However, since this flow dividing valve 17 produces a great pressure loss when the fluid passes through it, the hydraulic motors 14, 15 have the lower pressure applied. As a result, there is the problem that the rotational torque (traction force) is lower in the scene where a great traction force is required.